Coins need to be cleaned depending on the coin metal and according to
the dirt, crustation, and/or oxidation present on the coin. We have attempted
to break down the different methods and show some examples of the types of
uncleaned coins and the best method for cleaning them. Here are some favorite
methods used for cleaning coins:

This acid must be handled with care. It can be dangerous if safety
precautions not taken.

No

4

Tumbling

Good for more modern coins.

Can break, chip or crack coins.

No**

5

Electrolysis

Very Fast (Cleaned in a matter of minutes)

Can remove or discolor the patina.

No**

5

** In order to become proficient at this method of cleaning, I would
recommend practicing on some cull/broken coins.

Distilled Water (level 1)Technique:One of the gentlest
methods of cleaning coins is using distilled water (DW) soaks. This requires
that you soak the coin for 24 hours remove the coin and gently scrub the coin
with a soft toothbrush. Change the water and then repeat until the coin is
clean.

Theory:Distilled water contains almost no dissolved minerals.
When you put a coin in DW the minerals on the coin transfer to the water until
the DW is saturated with minerals.Good Candidates:

Soap and Water (level 1)Technique:Soak your coins in soap
and water and gently scrub the coin with a soft toothbrush. Repeat until the
coin is clean.Theory:Soap works by lowering the surface tension of
water allowing the water to penetrate the dirt, by emulsifying grease, and by
absorbing dirt into the foam. Good Candidates:

Olive Oil (level 1)Technique:Place your coins in a
container and cover coins completely with olive oil. Allow to soak for 1 to 6
months or longer. Change oil if it becomes discolored. After the soak period
clean the coins with soap and water and gently scrub the coin with a soft
toothbrush or clean mechanically if required. Repeat until the coin is
clean.NOTE: to clean the oil off of the coins a detergent specifically
designed to remove oil and grease may be required. Gringgotts Coin Cleaner has
been recomended. Do not use any cleaner that contains
chlorine.Theory:The oil penetrates the dirt and loosens it from the
coin.Good Candidates:

Mechanical Cleaning (level 2)Technique:Use brushes,
toothpicks, bamboo skewers, dried rose thorns, and for the more experienced
coin cleaner, battery-powered Dremel Diamond-dusted bits and dental picks to
loosen and remove dirt. Work from the outer edge of the coin to the center of
the coin.Theory:Using a tool to physically dislodge or scrape the dirt
off of a coin.Good Candidates:

Calgon® (level 3)Technique:Using a toothpick, apply
Calgon® to the oxidation and encrusted spots on the coin taking care not to
get the Calgon® on the patina. Let it set for a few minutes then rinse. Use
a toothbrush or a toothpick to dislodge the oxidation. Repeat until the coin is
clean.Theory:Calgon® is designed to be used as a water softener
with high mineral content water. Calgon® "removes" hard water minerals from
water.Good Candidates:

Ammonia (level 4)Technique:To make your own silver coin
cleaning solution, mix one part ammonia to six parts water. Soak coin in
solution then gently scrub the silver coin with a small soft toothbrush to
loosen dirt. Be careful not to scratch the metal. Always rinse after cleaning.
Repeat until the coin is clean. Be careful not to use ammonia on silvered or
fourree coins or coins with a high bronze content.Theory:An alkaline
gas composed of nitrogen and hydrogen. Aqueous solutions of with 5-10% ammonia
are sold as household ammonia. Best for cleaning oily dirt.Good
Candidates:

CLR (level 4)Technique:Best used as a spot application to
oxidation to soften and break it up. Do not allow it to come in contact with
the patina as the patina is a form of oxidation. Always rinse after cleaning.
Repeat until the coin is clean. Ususally the coin is corroded under the
oxidation and will have lost all detail.Theory:CLR is a diluted acid
that removes calcium, lime & rust.Good Candidates:

Ultrasonic (level 4)Technique:A home or commercial
ultrasonic cleaner unit is required to clean coins in this manner. Dip the coin
in solution for 1-3 minutes to clean the surface of the coin. Home units are
usually not powerful enough to clean heavily encrusted coins. Commercial
ultrasonic cleaners can be much more effective, but may damage the surface of
the coin and leave it pitted.Theory:Ultrasonic cleaning applies
intense, high-frequency sound to liquids, producing intimate mixing and
powerful chemical and physical reactions. The process ("cavitation") is, in
effect, "cold boiling" and results from the creation and collapse of countless
microbubbles in the liquid, producing shock waves.Good Candidates:

Formic Acid (level 4)Technique:A solution of 5-30 percent
formic acid in de-ionized water is effective for dissolving copper compounds
without affecting silver chlorides. Formic acid can also be used to brighten
silver that has already been cleaned with another chemical or technique.
Theory:Cupric oxide disloves and horn silver flakes off with gentle
cleaning. For the best description on how to use formic acid please refer to
the following page:http://nautarch.tamu.edu/class/anth605/File13.htmGood
Candidates:

Always read and follow manufacturer directions that come with any
chemicals.

Tumbling (level 5)Technique:Using special tumbling medias
such as pecan shells or stainless steel shot, the coins are mixed in and
tumbled until they are clean. This process can damage ancient coins but is very
good when used on modern coins that have not been subject to centuries of
corrosion.Theory:Rotary or vibratory tumbler is used to knock dirt and
deposits off of the surface of the coin.Good Candidates:

Electrolysis (level 5)Technique:Electrolysis is a very
quick and efficient way of cleaning coins, unfortuantely, it will often clean
the patina off the coin. Electrolysis can clean a coins so well that it will
reveal pitting and scarring that may not have been visible under the dirt or
patina. Because of the dangerous chemicals given off when using salt
(chlorine) as an electrolyte and stainless steel (chromium) as a cathode or
annode, it is highly recomended that sodium carbonate or sodium bicarbonate
(baking soda) are used instead of salt and carbon or copper conductors instead
of stainless steel. You should never use any solution that contains chlorine
around coins as it will damage the coin and promote bronze disease in bronze
coins.

In order to make a simplest of electrolysis machines you will
need a 9V battery, 2 copper wires, distilled water, and baking soda. 1. Mix
one tablespoon of baking soda in about 1 pint of water.2. Connect one
copper wire to the positve (+) end of the battery and put the other end in the
baking soda solution with the insulator stripped back about an inch.3.
Connect the other copper wire to the negative (-) end of the battery and wrap
the other stripped end of the copper wire around the coin so that it makes a
good connection to the coin.4. Put the coin on the wire in the baking soda
solution, but not touching the other wire.5. The coin and wire should begin
to bubble and the dirt and corrosion should loosen and fall off.6. After a
few minutes, remove the coin and gently clean with a paper towel.7. Repeat
if necessary.Even the best "zapped" coin takes a lot of work, and specialty
tools, to complete the "after-electrolysis" cleaning and final
preservation.

To learn more about using electrolyisis to clean coins and
how to make or purchase a better electrolysis setup, please visit
CoinZappers

Theory:The electrolytic process
requires that an electrolyte, an ionized solution (such as sodium carbonate or
sodium bicarbonate in distilled water), complete an electric circuit between
two electrodes. When the electrodes are connected to a source of direct current
one, called the cathode, becomes negatively (-) charged while the other, called
the anode, becomes positively (+) charged. The positive ions in the electrolyte
will move toward the cathode and the negatively charged ions toward the anode.
This migration of ions through the electrolyte constitutes the electric current
in that part of the circuit. The migration of electrons into the anode, through
the wiring and an electric generator, and then back to the cathode constitutes
the current in the external circuit.**

For example, when electrodes are
dipped into a solution of hydrogen chloride (a compound of hydrogen and
chlorine) and a current is passed through it, hydrogen gas bubbles off at the
cathode and chlorine at the anode. This occurs because hydrogen chloride
dissociates (see dissociation ) into hydrogen ions (hydrogen atoms that have
lost an electron) and chloride ions (chlorine atoms that have gained an
electron) when dissolved in water. When the electrodes are connected to a
source of direct current, the hydrogen ions are attracted to the cathode, where
they each gain an electron, becoming hydrogen atoms again. Hydrogen atoms pair
off into hydrogen molecules that bubble off as hydrogen gas. Similarly,
chlorine ions are attracted to the anode, where they each give up an electron,
become chlorine atoms, join in pairs, and bubble off as chlorine
gas.**

Good Candidates:

Coin preservation:

The best way to preserve you coin is with Renaissance Micro-Cryystalline
Wax Polish, used by the British Museum. One 200ml can will last a lifetime.
Other methods include: Kiwi Neutral Shoe Polish and other waxes.

Here are some basic facts about cleaning inorganic deposits:

Inorganic deposits: For our definition, inorganic deposits are: deposits
that are soluble (can be dissolved) but are not alive and did not come from a
living organism.